water pressure high and surging

[jrocksho]

1990 mercury 150 xr4. i just changed water pump assy, engine was overheating at idle and cold while running. i just bought and will be changing both t-stats and poppet assy. i was wondering if there's anything else i should look at to fix this. i think the t-stat or poppet is the problem. thanks. at idle, water pressure jumps from 3psi-10psi and while running at 5000rpms it holds at 25psi then jumps to 30psi and back to 25psi. temp gauge while running is pegged on cold, idle thru an idle zone and it warms up too much.

 

[Chris1956]

Re: water pressure high and surging

25-30 PSI for a Merc is unheard of. It is way too high. It sounds like the poppit is bad. And if Poppit doesn't open properly, and you don't overheat, I would suspect the thermostats as well.

let us know what you find (or don't find).

 

[jrocksho]

Re: water pressure high and surging

i do get about 23-25psi wide open usually, but not at 5000rpm i never seen my pressure do this before. the stats look fine, only about 2 years old and i have been in brackish water but they are not corroded or stuck. i will still replace them and poppet and wil let you know. thanks

 

[Chris1956]

Re: water pressure high and surging

Well, I have a '93 135HPV6, and I am dancing in the aisles with 10+ PSI, at high speed. I still think it is the poppit.

 

[Faztbullet]

Re: water pressure high and surging

Are you sure its a Xr4 powerhead? If its a older style powerhead 20-25 psi @5000 is right in the ball park due to poppet design. The newer motors 12 psi in minimum you want @5000rpm.

 

[jrocksho]

Re: water pressure high and surging

it says xr4 on the cover, it is an xr4 for sure. 20-25 is not the problem if it would stay stable, it surges between 30 and 20 psi. all i have left is to replace poppet. im hoping to change before this weekend, im ready to go fishing!

 

[Faztbullet]

Re: water pressure high and surging

The cover dont mean it hasnt been replaced with something different under it. How many bolt in poppet cover? Does it have return line to top of block?

 

[jrocksho]

Re: water pressure high and surging

4 bolts hold poppet cover. i changed everything last week, but didn't have a chance to test yet. the poppet spring did have some black residue built up on the ends, looked to me like paint. i think the last person that changed the poppet, repainted the cover and inner plate. i was off yesterday but spent all day in new orleans for mardi gras. i will be going fishing this weekend and i will let ya'll know if problem is solved. thanks again for the info. if this don't solve the problem, i guess i'll pull the pump assy, maybe i did something wrong but its simple and i've done this job several times with no problems at all. but we all make mistakes right??..lol.

 

[jrocksho]

Re: water pressure high and surging

i changed poppet and t-stats. although there's no more overheating symptoms, i still feel my pressure is too high. it was about 28psi @ 5500rpms and very cold water temps while running, but everything is normal while idling.